With Aaron Cook down and Clay Buchholz struggling, a look at Red Sox rotation depth

Aaron Cook was the insurance option. And now, at least for the immediate term, he’s not.

After the right-hander suffered a nasty gash just below his right knee on Saturday that led to 11 stitches (the entire Sox pitching staff was examining the pitcher’s battle scar this morning), he’s on the 15-day disabled list. And so, at a time when the Red Sox are in their third game of a 20 games in 20 days stretch, when Josh Beckett is considered healthy but just had to be skipped due to a lat issue and when Clay Buchholz struggling to the worst ERA in the majors, it is worth asking: Who’s next?

Daisuke Matsuzaka would be the most obvious option given that he is a starting pitcher who is on the team’s 40-man roster. Still, he is just two starts into his minor league rehab assignment after not having pitched since last June. He got his feet wet in Salem while allowing three runs in four innings while striking out three and walking two, then had a strong outing for Double-A Portland last weekend, allowing one run in 4 2/3 innings while striking out seven and walking two before hitting his pitch limit. Matsuzaka is expected to need at least two more starts in the minors, both to build his pitch count and to sharpen his command, before he would be a consideration for starting duty.

Beyond Matsuzaka (and, more precisely, until Matsuzaka is ready), the Red Sox almost certainly would have to rely upon a pitcher who is not on the 40-man roster if they needed a starter. Right now, the top candidate based on performance would be Justin Germano. The 29-year-old made a favorable impression during spring training, during which he tossed three scoreless innings. To date, he has been the most consistent starter in the PawSox rotation, having pitched at least five innings and yielded two or fewer runs in each of his six starts. In 33 1/3 innings, he is 3-1 with a 2.16 ERA, 22 strikeouts and three walks while allowing opponents to hit just .211.

That performance is consistent with Germano’s resume as a pitcher whose terrific command (he struck out 39 and walked four in 49 minor league innings last year), pitch mix and feel on the mound but lack of plus stuff has made him a Four-A pitcher for most of his career. He made 23 starts with the Padres in 2007, but otherwise has been up and down with just 13 additional starts in his career.

Beyond Germano, the Sox have a pitcher in Ross Ohlendorf with better stuff and a higher ceiling (as recently as 2009, he went 11-10 with a 3.92 ERA in 29 starts for the Pirates). However, he signed a minor league deal with the Sox this winter after going 2-14 with a 5.14 ERA over the last two years. Though he was hit around in his most recent start (five runs in three innings), prior to that, he had a 3.04 ERA, 14 strikeouts and four walks in his first four starts of the year. Ohlendorf has a June 1 opt-out in his minor league deal.

It’s a less-than-ideal depth equation for the Sox, something that reflects, in part, on the fact that the bullpen blueprint was blown up almost as soon as the season started. With Andrew Bailey out for four months and Mark Melancon in the minors, the Red Sox don’t have the same flexibility that they might have to consider Alfredo Aceves or perhaps Vicente Padilla as a starting option.